/*
 * Created on Dec 30, 2005
 * Created by Alon Rohter
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */
package org.gudy.azureus2.core3.util;

import java.security.SecureRandom;
import java.util.Random;

import org.gudy.azureus2.core3.config.COConfigurationManager;

/**
 * @author MjrTom 2006/Jan/02: added various methods, including some java.util.Random method aliases
 */

public class RandomUtils {
    public static final Random RANDOM = new Random(System.currentTimeMillis());

    public static final String INSTANCE_ID;

    static {
        byte[] bytes = new byte[3];

        RANDOM.nextBytes(bytes);

        INSTANCE_ID = Base32.encode(bytes).toLowerCase();
    }

    public static final SecureRandom SECURE_RANDOM = new SecureRandom();

    /**
     * Generate a random array of bytes.
     * 
     * @param num_to_generate
     *            number of bytes to generate
     * @return random byte array
     */
    public static byte[] generateRandomBytes(int num_to_generate) {
        byte[] id = new byte[num_to_generate];
        RANDOM.nextBytes(id);
        return id;
    }

    /**
     * Generate a random string of charactors.
     * 
     * @param num_to_generate
     *            number of chars to generate
     * @return random char string
     */
    public static String generateRandomAlphanumerics(int num_to_generate) {
        String alphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

        StringBuffer buff = new StringBuffer(num_to_generate);

        for (int i = 0; i < num_to_generate; i++) {
            int pos = (int) (RANDOM.nextDouble() * alphabet.length());
            buff.append(alphabet.charAt(pos));
        }

        return buff.toString();
    }

    public static final int LISTEN_PORT_MIN = 10000;
    public static final int LISTEN_PORT_MAX = 65535;

    /**
     * Generate a random port number for binding a network IP listening socket to. NOTE: Will return a valid non-privileged port number >=
     * LISTEN_PORT_MIN and <= LISTEN_PORT_MAX.
     * 
     * @return random port number
     */

    public static int generateRandomNetworkListenPort() {
        return (generateRandomNetworkListenPort(LISTEN_PORT_MIN, LISTEN_PORT_MAX));
    }

    public static int generateRandomNetworkListenPort(int min_port, int max_port) {
        if (min_port > max_port) {
            int temp = min_port;
            min_port = max_port;
            max_port = temp;
        }

        if (max_port > LISTEN_PORT_MAX) {

            max_port = LISTEN_PORT_MAX;
        }

        if (max_port < 1) {

            max_port = 1;
        }

        if (min_port < 1) {

            min_port = 1;
        }

        if (min_port > max_port) {

            min_port = max_port;
        }

        // DON'T use NetworkManager methods to get the ports here else startup can hang

        int existing_tcp = COConfigurationManager.getIntParameter("TCP.Listen.Port");
        int existing_udp = COConfigurationManager.getIntParameter("UDP.Listen.Port");
        int existing_udp2 = COConfigurationManager.getIntParameter("UDP.NonData.Listen.Port");

        int port = min_port;

        for (int i = 0; i < 100; i++) {
            int min = min_port;
            port = min + RANDOM.nextInt(max_port + 1 - min);

            // skip magnet ports

            if (port >= 45100 && port <= 45110) {

                continue;
            }

            if (port != existing_tcp && port != existing_udp && port != existing_udp2) {

                return port;
            }
        }

        return (port);
    }

    /**
     * Generates a random +1 or -1
     * 
     * @return +1 or -1
     */
    public static int generateRandomPlusMinus1() {
        return RANDOM.nextBoolean() ? -1 : 1;
    }

    public static float nextFloat() {
        return RANDOM.nextFloat();
    }

    public static void nextBytes(byte[] bytes) {
        RANDOM.nextBytes(bytes);
    }

    public static void nextSecureBytes(byte[] bytes) {
        SECURE_RANDOM.nextBytes(bytes);
    }

    public static byte[] nextSecureHash() {
        byte[] hash = new byte[20];

        SECURE_RANDOM.nextBytes(hash);

        return (hash);
    }

    public static byte[] nextHash() {
        byte[] hash = new byte[20];

        RANDOM.nextBytes(hash);

        return (hash);
    }

    public static int nextInt(int n) {
        return RANDOM.nextInt(n);
    }

    public static byte nextByte() {
        return (byte) RANDOM.nextInt();
    }

    public static int nextInt() {
        return RANDOM.nextInt();
    }

    public static int nextAbsoluteInt() {
        return ((RANDOM.nextInt() << 1) >>> 1);
    }

    public static long nextLong() {
        return RANDOM.nextLong();
    }

    public static long nextLong(long n) {
        if (n > Integer.MAX_VALUE) {

            while (true) {

                long rand = nextAbsoluteLong();

                long res = rand % n;

                // deal with non-uniformity as rand not generally divisible by n

                if (rand - res + (n - 1) >= 0) {

                    return (res);
                }
            }
        }

        return ((long) RANDOM.nextInt((int) n));
    }

    public static long nextAbsoluteLong() {
        return ((RANDOM.nextLong() << 1) >>> 1);
    }

    public static long nextSecureAbsoluteLong() {
        while (true) {

            long val = Math.abs(SECURE_RANDOM.nextLong());

            if (val >= 0) {

                return (val);
            }
        }
    }

    /**
     * @return random int between 0 and max-1. e.g. param of 10 returns 0->9
     */
    public static int generateRandomIntUpto(int max) {
        return nextInt(max);
    }

    /**
     * @return random int between min and max, e.g params of [5,7] returns 5,6 or 7
     */
    public static int generateRandomIntBetween(int min, int max) {
        return min + generateRandomIntUpto(max + 1 - min);
    }
}
